Resonant reed relay



Aug. 27, 1963 K. OZONE RESONANT REED RELAY Filed Feb. 2, 1959 CONTROLLEDDEVICE CONTROLLED DEVICE INVENTOR. KO HO OZONE BY 0L) ATTORNEY UnitedStates Patent "ice I 3,102,214 RESONANT REED RELAY Koho Ozone, Webster,N.Y., assignor to General Dynamics Corporation, Rochester,N.Y.,acorporation of Delaware Filed Feb. 2, 1959, Ser. No. 790,750

4!- Claims. (Cl. 317-447) This invention relates to relay ticularly tofrequency sensitive relays.

Frequency sensitive relays are widely used in receivers found inselective signaling and selective calling systems. Receivers of thesesystems have an assigned call signal of a particular frequency or acoded call signal containing a plurality of frequencies and one or morefrequency sensitive relays which are tuned to the frequency-orfrequencies of the assigned call signal.

The resonant reed relays of the prior art are characterized by theinclusion of the resonant reed as one element of the magnetic circuit.Due to the inclusion of the reed the magnetic circuit, the air gapformed between the vibrating end-of the reed and thecore structure ofthe relay presents a variable reluctance in the magnetic circuit whichresults in a nonuniform relationship between the driving current and theforce exerted upon the reed. This nonlinear relation between the drivingcurrent and the driving force is evidenced by the relay having anunsymmetrical frequency response curve. This phenomena which is known asthe hook effect makes it extremely difi'icult to obtain the requiredselectivity and stability of resonant frequency. The resonantfrequencies of such relays vary in accordance with changes, of strengthof the permanent biasing magnet, the size of the air gap, and thepresence of stray fields.

An object of this invention is to provide an improved frequencysensitive relay using simple and reliable components to thereby insurereliable operation.

- It is a further object of this invention, to provide a he quencysensitive relay having a stable resonant frequency.

'It is a further object of this invention to provide a frequencysensitive relay having a frequency response curve free from theso-called hook effect.

Further objects and advantages of the invention will become apparent asthe description proceeds and the features of novelty which'characterizethe invention will be pointed out with particularity in the claimsannexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to thedrawings in which:

FIG. 1 is a circuit diagram of one form of the invention'showing asectional top view of some of the components taken along line 1-1 inFIG. 2;

FIG. 2 is an end view of the components of FIG. 1;

FIG. 3 is a circuit diagram of a modified form of the invention showinga sectional top view'of some of the components taken along line 33 ofFIG. 4; and,

FIG. 4 is an end view of the components of the modified form of theinvention illustrated in FIG. 3.

The present invention contemplates that the call signal, which is to bedetected for control purposes, be applied to a resonant metallic reedwhich is supported for vibration within a constant magnetic field. Thus,when a call signal having a frequency equal to the resonant frequency ofthe reed is applied to the reed, it will cause it to vibrate at itsresonant frequency, due to the motor action of the sign-a1 currentswithin the magnetic field.

According to. my invention, it is possible to remove the metallic reedfrom the magnetic circuit since the signal currents are applied directlyto the reed rather than being indirectly applied by a winding upon thecore structure. In addition, this arrangement also allows the metallicdevices and more par- 3912,2 Patented Aug. 27, 1963 "I an resonant reedto be made of a nonmagnetic metallic conductor. Now, since the reed islocated in the steady field of a permanent magnet, a linear relationshipwill exist be tween the driving current and the driving forces exertedupon the reed. Thus, according to my invention, a resonant reed relay isprovided which is not subject to the hook effect, is extremely simple,and is not affected by stray fields, since the reed utilized within thisrelay can be made of nonmagnetic material.

According to the form of the invention of FIG. 1, the

metallic reed, when vibrating, makes intermittent contact with thestationary contact thus intermittently completing the relay work circuitwhich includes the contact, contact arm, and the reed; while themodified form of the invention, illustrated in FIG. 3, provides alocking action when energized.

Reference will first be made to FIG. 2 which illustrates the relativeposition of reed 2, magnet 1, and contact 3, as seen in an end view ofthese elements. Means are provided for supporting reed 2, in a mannerhereinafter to be described, within the aperture of magnet 1 withsufficient clearance being provided on both the top and the bottom ofthe reed so that it will not strike magnet *1 when it is set intovibration. Contact arms '16'is provided for suporting contact 3 abovereed :2 a sufficient distance so that contact 3 will not come intocontact with reed 2, unless reed 2 is set into vibration.

Referring now to FIG. 1, source 12 is used to represent any source ofcall signals, a particular frequency of which is desired to be utilizedas a control signal. Thus, when this invention is utilzed in a selectivecalling or signaling system, source 12 represents the antenna anddemodulator circuits for detecting the call signals imposed upon thecarrier.

The call signals provided by source 12 are applied to primary winding 11of transformer 9-which has a stepdown turns ratio in order that thecurrent generated in the secondary will be of sufficient magnitude toproperly drive reed .2. Reed 2-WhlCl1 consists of a thin strip ofmetallic nonmagnetic material having a natural resonant frequency equalto the frequency of the call signal has a slot cut in one end thereof,thereby forming legs 5 and 6. Leg 6 is connected to one side ofsecondary winding Ill by capacitor 8, while leg 5 is connected to theother terminal of secondary winding 10 by conductor 7. Thus, a drivecircuit is established for reed 2 from one side of secondary winding :10through capacitor 8, leg 6, reed 2 at base 17 of the slot, leg 5, andconductor 7 back to the other side of secondary winding \10. Capacitor"8 is provided to resonate with the inductance of winding 10 at theresonant frequency of reed 2 in order that the current flowing in thereed drive circuit will be maximum at that frequency.

The motor action necessary to drive reed 2 is provided by theinteraction of the call signal currents flowing in the drive circuit atarrow 15, with the magnetic field at that point. Since the currentspassing between legs 5 and 6 of reed 2 will have a major component ofcurrent flowing perpendicular to the lines of flux of the field, reed 2will be set into vibration.

Clamp 4- is provided to support reed 2 within the magnetic fieldassociated with magnet 1, in a manner hereinbefore described withrelation to FIG. 2, by clamping legs 5 and 6 of reed 2 in a conventionalmanner to a supporting surface (not shown). Clamp 4 also provides meansto position reed 2 within the aperture of magnet 1 so that the area ofmaximum current density at arrow 15 lies approximately halfway betweenback surface 18 and front surface 19 of magnet 1. When reeds 2 is sopositioned with respect to the magnetic field, the current at arrow 15will be within the portion of the field of maximum flux density andconsequently will link a maximum due to linking "flux in front of frontsurface 19.

I forces.

' 21 which'are connected in series with leg 6, the portion of reed 2 atbase 17 of the slot, contact 3 and contact supporting arm 16.; Due tothe blocking action of capacitor 8, no D.C. currents will flow in leg 5.Armll6 is positioned coaxially with leg 6 so that the DC. currentpassing throughthe fieldwill exert no net forces upon reed 2 to hinderits vibration since the DC. path is generally parallel to the lines offiux in the area of greatest flux density at arrow 22. In addition, noforces will be exerted upon reed Z due to the D.C. current linking thelines of'flux outside of magnet 1, since the field is generallysymmetrical and the forces due to linking flux behind back surface 18Will be equal and opposite to the forces Therefore, the'passage of theDC. control currents through the field does not interfere with the reeddriving action of the call signal currents.

Reference will now be made to the embodiment of FIGS. 3 and 4, where thesame reference numerals are used to identify elements corresponding withthose of the embodimentof'FIGS. land 2. 'In'this embodiment, contactsupporting arm 16 is positioned so that contact 3 will make with leg 6vwhen reed Z'i s vibrated. The emwhen said signal currents are of afrequency equal to said resonant frequency; a DC current path includinga con tact and said reed and means for supporting said contact I adistance from said reed-such that said reed will make with said contactwhen said reed is deflected during vibration to thereby complete saidDC. current path, said contact supporting means being positioned withrelation to said reed such that the D.C.curr'ent path formed Within saidreed upon said contact making with said reed will link the lines of fluxofsaid magnetic field in sucha 1 manner as toexert no net force uponsaid reed.

2. A resonant reed relay comprising a metallic reed having a naturalresonant frequency, said reedhhavinga slot in one end thereof; means forproviding a magnetic field; means for connecting saidsignal input meansacross the slotted end of said reed tothereby cause signal currents toflow through said reed; means for supporting said reed in said magneticfield so that signal currents in said I reed are substantiallyperpendicular to saidfield to thereby cause said reed to vibrate whensaid signal currents are of a frequency equal to said resonantfrequency; a. contact; a DC. current path including said contact and aportion of said reed; means for supporting said contact a distancefromsaid'reed such that said reed will make with said contact when saidreed starts to vibrate to thereby complete said DC current path, saidcontact supporting means being positioned with relation to said reedsuch that the DC. current path formed within said reed upon said contactmaking with said reed will link sufficient lines bodiment of FIGS. 3 and4 differs fromthe embodiment of FIGS. 1 and 2 since controlled device 20is connected toleg-S rather than legd. The external series circuit ofcontrolleddeviceztl and DC. source '21 is now connected in serieswithleg 5-, reed 2 at base 17 of the slot, a portion of leg 6, contact3, and supporting'arm 16. Thus, the DC. path Within reed 2 will now passthrough the area of maximum flux. density near base 17. When source 21is polarized as indicated, current will flow through the region ofmaximum fluxv density in a direction indicated by arrow 22. Thiswillresult in exerting a force on reed 2 tending to hold it againstcontact 3. Locking action may thus be accomplished by providing a DC.current of sufiicient magnitude sothatthe net current linking the linesof flux of the field is sufficient tohold reed 2 during reversals of thecall signal currents.

The particular embodiments of the invention illustrated and describedherein is illustrative only and the inven- 7 tion includes. such othermodifications and equivalences as may readily appear to those skilled inthe art; for example, capacitor can be dispensed with in both embodiments if sufiicient call signal current can be transferred tothe'reed to exert .the necessary reed driving However, if capacitor 8'of FIG. 1 is dispensed with, contact supporting arm 16 should bepositioned coaxially with the slot. In this way, any net force thatmight be exerted on reed 2 due to current from leg 6 linking'some linesof flux will be cancelled by an equal .and opposite force due to thecurrent of leg 5. If capacitor 8 of FIG. 3 were dispensed with, thevoltage of source 21'would have to be increased in order to maintain thelooking current at its proper magnitude. 'It is further V noted that Ido not intend to be limited to the use of nonslot inone end thereof;means: for providing a magnetic field; means for applying signals'acrosssaid slotted end to thereby cause signal currents to flow through saidreed; means forsupporting said reed in said magnetic field so thatsignal currents in said reed are substantially 'perpen dicular to saidfield to thereby cause said reed to vibrate of flux of said field sothat when current of proper polarity transverses said current path saidreed will be maintained against said contact during reversals of saidsignal currents.

3. A resonant reed relay comprising a metallic reed having a naturalresonant frequency, said reed having aslot in one end thereof; means forproviding a magnetic field; inductive signal input means; |a capacitor;means for connecting said signal input means andsaid capacitor in seriesacross the slotted end of said reed, said capacitor being of such valueto resonate with theinductance of said signal input means at thefrequency of resonance of said reed; means for supporting said reedfatsaidslotted end, said supporting means being positioned with respect tosaid magnetic field so that the signal curents flowing in said reed-atthe base of said slot are substantially perpendicular to said magneticfield to thereby cause said, reed to vibrate when the frequency of thesignal currents are equal to the resonant frequency of said reed; acontact; a DC. current path including said contact and a portion of saidreed; means for supporting said contact in proxi mity to said reed sothat said need will make with said contact when said reed is setintovibration to thereby complete said DC. current path, said contactsupporting means being positioned with relation to said reed such thatthe DC. current path formed within saidfreed upon said contact m akingwith said reed will link thelin'es of flux of said magnetic field insuch a manner as toexert no net force upon said reed when D.C.currentstraverse said path. V Y I 4. A resonant reed relay comprising a metallicreed having a natural resonant frequency, said reed having a slot in oneend thereof; means for providing a magnetic field; inductive signalinput means; a capacitor; means for connectingsaid signal input meansand said capacitor in series across the slotted end ofsaid reed, saidcapacitor :being of such valueto resonate with the inductance of saidsignal input means at the frequency of resonance of. said reed; meansfor supporting said reed at said slotted end, said supporting meansbeing positioned'with respect to said magnetic field so that the signalcurrents flowing in vsaid reed at the base of said slot aresubstantially perpendicular to said magnetic field to thereby cause saidreed to vibrate when the frequency of the signal currents are equal tothe resonant frequency of said reed; a contact; a. DC. current pathincluding said contact and a portion of said reed; rneans'for supportingsaid contact in proximity to said reed so that said reed will make withsaid contact when said reed is set into vibration to thereby completesaid D.C. current path, said contact supporting means being positionedwith relation to said reed such 5 that the D.C. cuirent path formedWithin said reed upon said contact making With said reed will linksuflicient lines of flux of said field so that when current of properpolarity tr-ansverses said current path said reed will be maintainedagainst said contact during reversals of said 10 signal currents.

References Cited in the file of this patent UNITED STATES PATENTS LovellAug. 17, 1943 Adler Feb. 3, 1948 Rieber May 10, 1949 Welker Nov. 15,11955 Sihvonen Mar. 1, 1960 FOREIGN PATENTS Germany Oct. 13, 1934 GreatBritain Feb. 11, 1953

1. A RESONANT REED RELAY COMPRISING A METALLIC REED HAVING A NATURALRESONANT FREQUENCY, SAID REED HAVING A SLOT IN ONE END THEREOF; MEANSFOR PROVIDING A MAGNETICFIELD; MEANS FOR APPLYING SIGNALS ACROSS SAIDSLOTTED END TO THEREBY CAUSE SIGNAL CURRENTS TO FLOW THROUGH SAID REED;MEANS FOR SUPPORTING SAID REED IN SAID MAGNETIC FIELD SO THAT SIGNALCURRENTS IN SAID REED ARE SUBSTANTIALLY PERPENDICULAR TO SAID FIELD TOTHEREBY CAUSE SAID REED TO VIBRATE WHEN SAID SIGNAL CURRENTS ARE OF AFREQUENCY EQUAL TO SAID RESONANT FREQUENCY; A D.C. CURRENT PATHINCLUDING A CONTACT AND SAID REED AND MEANS FOR SUPPORTING SAID CONTACTA DISTANCE FROM SAID REED SUCH THAT SAID REED WILL MAKE WITH SAIDCONTACT WHEN SAID REED IS DEFLECTED DURING VIBRATION TO THEREBY COMPLETESAID D.C. CURRENT PATH, SAID CONTACT SUPPORTING MEANS BEING POSITIONEDWITH RELATION TO